Mangrove Forests

Special issue on "Mangrove Forests" by the Journal "Natural Resources and Development". Published by Institute for Scientific Co-operation, Tbingen, Germany, 1996 (Not Priced), 145 pages.

This is being reviewed here since the topic of the special issue has strong affinity to the theme of our ENVIS Centre. There are five key contributions dealing with mangroves in Asia including India. The book has five contributed chapters :

    1. Mangroves - Forgotten Forests ? : by Ralf Schwamborn and Ulrich Saint-Paul.

    2. Destruction of mangrove Wetlands - Causes and Consequences : by Michael Mastaller.

    3. From Traditional Use to Total Destruction - Forms and Extent of Economic Utilization in the Southeast Asian Mangroves : by Dieter Uthoff.

    4. Effect of Sea Level Rise on the Mangrove Ecosystem in Thailand : by Sanit Aksornkoae and Nittharatana Paphavasit.

    5. The Mangrove Populations of Vietnam and the Development of their Exploitation : by Holm Uibrig.

Are mangroves - forgotten Forests ? - This question is addressed elegantly by Ralf Schwamborn and Ulrich Saint-Paul in Chapter-1. The world wide distribution of mangroves coincide with the 20 C - winter isothermal lines. The riverine mangroves, predominantly in their estuarine region, are the more commonly studied one. According to 1993 data compiled by the authors, out of a World total of 14200x103 ha mangroves only a very small percentage (2.54% about 360x103 ha) is now preserved in India while Indonesia, Malaysia together account for about 37% of the mangrove forests.

Mastallier (Chapter-2) categorise the various causes that have resulted in the progressive destruction of mangroves world wide. In Kerala alone, the mangrove area has come down from 70,000 ha in 1911 to 250 ha in 1989 whereas in Malaysia and Indonesia nearly 50% of the original mangrove area has been lost in the recent years. Both natural events, such as tidal cycle, or anthropogenic activity such as agriculture, shrimp farming etc. are responsible for this loss. The author states that in a single tidal storm are 5 m in Bangladesh, 8.5 million trees of a single predominant tree species was destroyed in 1988. The development of Bombay since 1670 for urban settlement has progressively eliminated the mangroves forest there.

Uthoff (Chapter-3) tabulates the progressive loss of mangroves in South East Asia from historical times. The author shows that in Thailand, in the three decades 1961-1971, the loss is about 18 ha per day or an equivalent loss of 65 km2 every year. In Philliphines, within a single decade of 1981-1991, about 785 km2 of mangroves area has been converted to agriculture.

Aksornkoae and Paphavasit (Chapter-4) critically discusses the effect of rising sea levels on the survivability of various mangrove species in Thailand.

Uibrig (Chapter-5) summarises the mangrove history in Vietnam. From 1943 to 1991, the mangrove area has come down from 4,09,000 ha to 1,60,000 ha. In the Mekong delta alone, out of a total forest area of about 5,63,000 ha, 5,03,000 ha is marked as a productive forest for cultivation and harvesting on diverse mangrove species and about 26,000 ha is reserved as a protected National Forest not to be tampered with.

The special issue tabulates over 500 references on mangrove forest, including the nutrient and biogeochemical status. The book is a valuable tool for researchers and is must for all biogeochemical work on mangroves. It is strongly recommended. Our ENVIS centre has a copy and selective chapter can be copied, with authors permission for distribution for academic use only.

V. Subramanian
School of Environmental Sciences
Jawaharlal Nehru University
New Delhi - 110 067


Water Analysis : User-friendly Field/Laboratory Manual

Water Analysis : User-friendly Field/Laboratory Manual by Silva, EIL; Namarathe, SY; Weerasooriya, SVR; Manuweera, L, Institute of Fundamental Studies, Hantana Road, Kandy, Sri Lanka, 1996, 193+v pp.

Water, the life-support of planet earth, is today under incredible pressures from a variety of use patterns generated by modern human civilisation. Degradation of this vital resources is primarily in the form of anthropogenic inputs, a feature which limits the use of water towards different ends. Therefore, knowledge of the physico-chemical and biological properties of water provides a basis for planning its end-use, rationalising its use pattern and minimising further deterioration. An insight into these properties is gained only through information on a vast array of parameters obtained by a variety of analytical methods.

This manual is an outcome of the project on quality assessment of surface water in Sri Lanka, sponsored by USAID and coordinated but the National Resources and Environment Policy Project/International Resources Group (NAREPP/IRG). It is unique in that it adapts a practical approach by taking into account the existing limitation in the availability of sophisticated instrumentation facilities in developing countries.

The manual includes six chapters. The first chapter briefly explains the theory behind most of the analytical procedures. This chapter also elaborates the over all procedures of specific analyses. The second chapter elaborates an important aspect of analytical work viz., maintenance of the instruments and glasswares. Most of the poor performance of instruments are solely due to their poor maintenance. The manual also provides a chapter on basic statistics which, when used to analyse data, points at the errors during experimentations. This would be very useful for technicians who actually handle the experimental part most often.

The accuracy and precision of analytical data depends on each and every step of sample analysis. The very first step is to identify stations where from representative samples could be collected. Then comes the question of sampling, processing and preservation of the samples. This manual has spend one full chapter on these vital issues. Analytical procedures for different parameters are given in chapter-5 in a unified manner. There is final chapter on quality control and other related issues.

The concentration of individual parameters, particularly metals, varies widely according to the kind of solutions (viz. fresh water, marine water, industrial effluent etc.). The specific wavelength in AAS always has an optimum working range, as also mentioned in the manual. The phenomenon of interference also varies from solution to solution. The use of the same wavelength for every kind of water analysis by AAS therefore increases the possibility of experimental errors (such as, in the process of diluting the samples, often to unreasonable extents). This manual, it seems, may be more comfortably used for analysis of samples from freshwater systems. Further, the manual has not taken into consideration the analysis of many trace metals viz., As, Hg, Se etc. which can be determined in AAS by using HG or by GF. These metals, often introduced through anthropogenic activities, present a serious threat to the biosystems. This manual, with the help of continuous feedback from the actual users, has the potential to evolve into a truly basic manual.

Dilip K Datta
Gujarat Ecological Society
Vadodara - 390007
S. Bandyopadhyay
Gujarat Ecology Commission
Vadodara - 390007


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